The pressure vessel of the above-described device is in the form of a small bottle. The volume of the bottle can be 5 to 50 ml. The outlet opening is provided at the upper end of the bottle. This outlet opening is, as a rule, closed by pressing a discharge element into the opening and/or by flange connecting the discharge element to the pressure vessel, for example, a metering valve having an upwardly projecting cylindrical hollow needle often with an elastic seal arranged between the head and the metering valve.
The pressure vessel is filled in such a manner that the substance to be emitted is first introduced through the metering valve or is introduced through the metering valve together with the propellent.
As preparation for administering, the pressure vessel is pushed into a cylindrical part having a delivery head. The cylindrical hollow needle of the metering valve is introduced form-tight into a cylindrical receptacle of the delivery head. The receptacle is hollow and communicates with a channel. As a rule, the channel opens into an opening which is in the end of the delivery head and is configured as a spray head.
The delivery head can have a mouth or nose piece which can be protected against contamination with the aid of a cap mounted thereon.
In the known device, the pressure vessel projects with the delivery head from the bottom of the cylindrical part.
The metering valve can be activated in that the user presses from above with the index finger against the delivery head and against the pressure vessel with the thumb from below. This then triggers the metering valve thereby emitting a defined quantity of active substances via the nozzle head.
The known pressure vessel made of glass is covered with a coating of a transparent plastic. This coating is intended to protect against splinters when the vessel bursts and therefore comprises a flexible soft plastic, such as PVC having a high expansion. The high expansion is important because the inner pressure acts on the soft plastic in the case that the glass vessel bursts. If the soft plastic could not yield with a change in volume in response to the pressure, then a sudden destruction of the plastic material could well occur because of disintegration or corrosion stress cracking.
The known arrangement affords the advantage that it permits a visual determination of the residual quantity in the pressure vessel of the substance to be supplied. This is so because both the pressure vessel and the enclosure are made of a transparent material (glass). This is of special significance in the administration of inhalation preparations which often have the nature of an emergency medication (for example, an asthma preparation). In this connection, the danger would otherwise be present that the pressure vessel could be empty in the event of an emergency.
In the known arrangement, it is disadvantageous that the transparent pressure vessel of glass is not sufficiently safe notwithstanding a coating with plastic in the case of an explosion, for example, because of incorrect handling. This insufficient degree of safety is present because the coating cannot prevent parts of the glass vessel from being propelled into the ambient in the manner of a projectile, especially in the region of the valve.
It is furthermore known to utilize pressure vessels made of metal materials. The bursting and splintering protection for such pressure vessels is effected by the advantageous characteristics of the selected material. These characteristics include high toughness and high strength.
It is a disadvantage of this device, however, that the opaque pressure vessel permits no visual determination of the residual quantity of the substance to be supplied which, in turn, brings with it the above-described disadvantages.